I did some stuff with the shaders. E.g. I tried to create some light flares, but I'm struggling a bit with that... Once I have exported the .gmt out of the Material Tool 2, rF tells me that there is a texture ("srpl-empty") missing on material 0 and the model doesn't load. 3dsimed says that there's a "Diffuse Map T3" at the material of the light flare, but no texture is assigned. My problem is, that I can't assign a texture in 3dsimed and save, because then, the flare won't be working any more at all.

srpl_empty.dds s located in SkyFiles folder - copy it from there and everything should work.

As for re-opening exported files in other tools it's not gonna work. These shaders go a little beyond what GMT files were meant for, so I'm using things like texture UV coordinates to store parameters like flare radius for example. Standard editors meant for rFactor won't be able to handle files exported from my tool. Whatever you export - it's final.

Of course you can still work on your meshes, by editing original GMT files (these without shaders) and when you load your project in my tool again - you will see all your changes. The only thing you need to do is re-export.

That's why this tool does not modify any GMT file you added to your project - they remain untouched on disk, so you can still work on them. New GMT files with shaders are exported to another folder.

EDIT:
I quickly prepared this image to show the idea:

On the left is some standard workflow - you work on .GMT files using some editor and then you put that file into rFactor.

On the right is workflow with my material tool - you work on .GMT files the same way, using 3D Studio and then let my tool add shaders on top of that, based on information in the project file.

What's marked in green are files you actually work on using these tools.

Currently, you can only use predefined animations I've provided (headlights, etc.).

Maybe I'll add a possibility to use custom animations on flares, maybe not

For now you can use a simple trick - make rotating flare, set constant radius and set blend angles very close to each other. I've used rotating flares for this safety car:

For afety car I've not used blend angles, so flares are alvays visible, but I've used high radius power for "flash" effect.
If you rather want weak, but flashing light, then flashing should be done with blend angles rather than radius.

1. See if your .gmt file is added correctly to .gen files - make sure the one you export is the one loaded in rFactor
2. Go to Project => Options and set light glow material name - name it MyCarFlare or something like that. This way your flare materials will be names MyCarFlare0, MyCarFlare1 and so on. Otherwise there may be some conflicts in materials.
3. Add alpha channel to your flare texture - my flare materials are based on alpha blending (do it later, when everything else works).

If anything elsse fails - let me know which version of shader pack are you using (although I believe this shader didn't change since first public version).

As for Rotation parameter it's radians/s, so values around 6.0 will give you like 1 flash per second (it's not accurate and rythm may change a little on different tracks and times of day).

In my case your .gmt was rotating on track.
In general, rotation works only on track and only when game is not paused. That's simply because rotation is controlled by time of day.

Of course by rotation I don't mean some kind of rotating texture etc. It's the flare direction vector that gets rotated. This will only affect radius or blending of a flare.

As for flare position - there can be two reasons.

First is graphical model offset and that's probably what's happening. If you're using graphical offset then make separate .gmt for track and showroom and manually add that offset value to flare coordinates in editor.
It will seem misplaced in editor, but will be in place in rFactor.

The other case is when .gmt file is set as debris. I don't know the exact rules of calculating debris mesh offset, so it may be inacurate sometimes. New version of editor allow manual corrections. But I don't think that's what's happening in your case.